In this chapter of our Car Mechanic Simulator 2021 guide we advise on the best course of action you can take if you run out of money in the middle of a commission. We advise on how to avoid running out of credits for the purchase of new parts.
Unfortunately, economics in Car Mechanic Simulator 2021 aren't too developed - if you run out of money in the middle of an order, there's not much you can do. You can't work with a negative cash balance, you can't take out an emergency loan either.
You should always remember not to go bankrupt no matter what. Make sure not to invest too much into expensive garage upgrades at first, and always have at least a few thousand credits at hand before starting a story commission. In the early game you won't have the backroom necessary for repairing parts, so you'll be forced to purchase new ones.
You also shouldn't save the game while repairing - in case something happens, you can reload and return to the period before starting the commission, then do some regular orders to raise your budget.
Your only real option to fill your wallet is accepting additional orders while working on the story one, as they require less money to finish. However, usually it's still not much help at all. Smaller orders often give you less than 50 CR, not really changing your situation too much.
We also recommend you to read the chapter How to earn money quickly? as it contains other ways to increase your budget aside from repairing cars.